Fuel additive for jet propulsion engines



Patented Oct. 30, 1962 3,061,419 FUEL ADDITIVE FOR JET PROPULSION ENGINES Roy C. Sias and Richard M. Tillman, Ponca City, Okla., assignors to Continental Oil Company, Ponca City, Okla, a corporation of Delaware No Drawing. Filed Oct. 2, 1958, Ser. No. 764,740 3 Claims. (Cl. 44-68) The present invention relates to hydrocarbon fuels for jet propulsion engines. More particularly, the present invention relates to the use of thermal stability additives for such fuels.

In modern aircraft, jet fuels are used as a heat sink to cool the engine lubricant. Depending on engine design, they are also exposed to marked heating by direct radiation from the burners flame in flowing to the fuel nozzles. These two heat sources result in fuel temperatures ranging up to 600 F. While residence time may be low, some fuel pyrolysis occurs and the pyrolysis products cause varnish-like deposits in fuel controls and physical plugging of filter screens or the fuel nozzles themselves. Such mishaps cause engine malfunction or, in extreme cases, failure.

While it may be possible, by careful selection of blending stocks, to alleviate this formation of pyrolysis products, usually this is not desirable for economic reasons. Also, it is possible to post-treat blending stocks, as for example by hydrotreating, to improve their thermal stability properties. This, too, is not desirable for economic reasons. Certain military specifications are very severe and it is very difiicult, if not practically impossible, to blend a fuel to meet these specifications without the use of an additive. Because of this and the aforementioned reasons, it would be very desirable to have an additive which enables fuels of marginal, and even poor, quality to pass the thermal stability specification.

Another requirement for fuels of this type is the water tolerance specification. The presence of water in turbojet fuels is very undesirable since it may cause ice crystal formation at the low temperatures encountered at high altitudes. This requirement is particularly relevant to the thermal stability requirement, since there are many additives which enable the fuel to meet thermal stability requirements but which adversely affect the water tolerance properties of the fuel.

It is an object of the present invention to provide a thermal stability additive for fuels for jet propulsion engines. It is still a further object of the present invention to provide a thermal stability additive for fuels for jet propulsion engines wherein the additive will not adversely lifect the water tolerance properties of the fuel.

It has been discovered that the use of aluminum diiydroxy dinonyl naphthalene sulfonate in minor amounts n hydrocarbon fuels enables the fuel to meet thermal stability requirements for jet propulsion engines and at .116 same time will not adversely affect the water tolerance )roperties of the fuel.

While the major use at present for this type of fuel is n turbojet engines, the present invention is not restricted this usage. The additives of the present invention Function satisfactorily in any hydrocarbon fuel for jet Jl'OPlllSlOIl engines.

Thermal stability of turbojet fuels and additives is evallated by a procedure which employs an apparatus known 18 the Erdco Fuel Coker, or as the CFR fuel coker. 30th the procedure and apparatus have been approved by he military, and specifications refer to results obtained sing this procedure. The apparatus essentially consists )f a porous sintered metal filter plug through which the uel to be tested is pumped at a specified rate and under :ontrolled temperature conditions. Fuel rate is usually pecified in pounds per hour. Separate temperature controls regulate the preheater and filter sections. Fuel temperatures are expressed in F. This apparatus approximates the coolant system of aircraft turbine-type engines. The thermal stability is determined by measuring the pressure drop (in inches of mercury) across the filter plug for a measured time interval and under specific fuel temperature and fuel rate conditions. Alternatively, it may be determined by measuring the time required to reach a measured pressure drop. This procedure is based on the assumption that pressure drop across the filter is a direct measure of the pyrolysis products either as to amount and/or particle size.

In this test, the minimum pass rating usually has been a minimum of 300 minutes with a maximum pressure drop of 25 inches (of mercury). More recently, there has been a tendency to make these requirements more strin- The water tolerance test is often referred to as the water emulsion test. The method of this test is described in Method 3251.5 of Federal Test Method Standard No. 791, which is entitled Interaction of Water and Aircraft Fuels. Briefly, the method involves the following procedure: a IOU-milliliter glass-stoppered graduated cylinder containing milliliters of the fuel sample and 20 milliliters of distilled water is shaken vigorously at room temperature for at least two minutes. It is then allowed to settle undisturbed on a vibration-free surface for a maximum period of five minutes. The volume of the aqueous layer is recorded to the nearest 0.5 milliliter. In order to pass, there must be no evidence of an emulsion, precipitate or suspended matter within or upon either layer. In addition, neither layer shall have changed in volume by more than 2 milliliters.

In order to disclose more clearly the nature of the present invention, the following illustrative examples will be given. It is to be understood that the invention is not to be limited to the specific conditions or details set forth in these examples except in so far as such limitations are specified in the appended claims.

In the examples, PDB refers to postdodecylbenzene, which is a by-product of the manufacture of dodecylbenzene, being the material distilling at a higher temperature than the dodecylbenzene. Somewhat more accurately postdodecylbcnzene consists of monoalkylbenzenes and dialkylbenzenes in the approximate ratio of 2:3. Its typical physical properties are as follows:

Specific gravity at 38 C 0.8649

Average molecular weight 385 Percent sulfonatable 88 A.S.T.M., .D-158 Engler:

I.B.P. F 647 5 F 682 50 F 715 90 F 760 F 775 F.B.P. F 779 Refractive index at 23 C 1.4900 Viscosity at:

l0 C. centipoises 2800 20 280 3 Aniline point C 69 Pour point F 25 Also, the term DNN refers to dinonyl naphthalene, which is prepared by alkylating nonene and naphthalene. The term 170 Pale Oil refers to a parafiinic lubricating oil fraction having an SSU viscosity at 100 F. of 170.

EXAMPLE I Preparation of Neutral Aluminum PDB Trisulfonate To a two-liter, three-necked flask equipped with stirrer, reflux condenser, thermometer, and dropping funnel were charged:

559.5 grams PDB sulfonic acid solution (0.5 1 milliequivalent per gram of sulfonic acid) 265 grams 170 pale oil This mixture was heated to 50 C. with agitation and the following solution then admitted through the dropping funnel over a fifteen-minute period:

20.4 grams aluminum isopropoxide 250 ml. benzene Following this addition, the reflux condenser was changed for distillation and the product stripped to 150 C. This preparation yielded 444 grams of a bright, somewhat viscous liquid, which had the following analysis:

Percent Al (weight) 0.61 Percent active 30.55

EXAMPLE II Preparation of Neutral Aluminum Hydroxy PDB Disulfonate The equipment and procedure used were the same as in Example I. The following materials were used:

373 grams PDB sulfonic acid solution (0.51 milliequivalent per gram of sulfonic acid) 174 grams 170 pale oil 1.8 grams water 20.4 grams aluminum isopropoxide 250 ml. benzene A yield of 292 grams of a bright, fluid product was obtained. The product has the following analysis:

Percent Al (weight) 0.92 Percent active 31.8

EXAMPLE III Preparation of Neutral Aluminum Dihydroxy DPB Sulfonate The equipment and procedure used were the same as in Example I. The following materials were used:

311 grams PDB sulfonic acid solution (0.51 milliequivalents per gram of sulfonic acid) 169 grams 170 pale oil 6 grams water 38 grams aluminum isopropoxide 300 ml. benzene A yield of 277 grams of a bright, fluid product was obtained. The product had the following analysis:

Percent Al (weight) 1.81 Percent active 30.2

EXAMPLE IV Preparation of Neutral Aluminum Dihydroxy DNN Sulfonate The equipment and procedure used were the same as in Example I. The following materials were used:

86.5 grams DNN sulfonic acid (1.04 milliequivalent per gram of sulfonic acid) 4.5 grams 170 pale oil 100 ml. benzene (Step I) 2.25 ml. water 19.4 grams aluminum isobutoxide ml. benzene (Step II) The product from this reaction was hazy. centrifuging yielded a bright, fluid product, which had the following analysis:

Percent Al (weight) 2.6 Percent active 50.0

EXAMPLE V Erdco and Water Emulsion Testing The products of Examples I and IV Were added to jet fuel base stocks and subjected to the Erdco test. Concentration (in parts per million) varied from 15.63 to 62.5. The results are shown in Table I.

.In addition, water emulsion tests were run on the above blends of additive in base stock. These results are also shown in Table I.

EXAMPLE VI Erdco Testing of Commercial Additives Several commercial heating oil additives were blended in a jet fuel base stock at a concentration of 500 parts per million. Their blends were then subjected to Erdco testing. The results are shown in Table II.

TABLE L-ERDCO AND IVATER EMULSION DATA Thermal Sta- Water Emulsion Test bility Test Concen- Additive tration in Fuel Pres- Time (p.p.m.) sure in Min- Ml. M1. Rating Drop, utes Unit 11 0 III. Hg

giant]! (in 25 25 0 20 Pass on re a u um PDB trisulfouate, 3 3 28 1 Fall 0.61% Al. leutml aluminum. 62. 5 0.1 600 25. 5 2 Fall.

hydroxy PDB di- 31 25 25 143 sullonate, 0.92% Al. Neutral aluminum 62. 5 6. 6 600 30 0 Fall. dihydroxy PDB 31. 25 5. 8 600 20. 5 8 Fail. sulfonate, l.81% Al. 15. 63 25 29 4 19 Fail. Neutral aluminum 62. 5 0 300 0 20 Pass dihydroxy DNN 31. 25 5. 4 300 1 19 Pass sulfonate, 2.6% A]. 15. 63 0 20 Pass Conditions:

Preheater tem- 400 F.

peraturc. Filter tempera- 500 F.

ture. Fuel rate t} 4)1b./hr. (which is more severe than 6 lb.[hr. due to longer residence lme TABLE IL-ERDCO DATA-COMIVIERCIAL ADDIIIVES Thermal Sta- Concenbility Test tration Additive in Fuel (p.p.rn.) Pressure Time Drop, in Min- In. Hg utes Enjay Paradyue IIO-2 500 25 41 Sautolene H 500 25 65 Sautolene .I 500 25 61 Granite F0 Dis 500 25 166 Tretolize FOA 500 25 222 The data presented in Table I show that neutral aluminum dihydroxy PDB sulfonate has superior properties as a thermal stability additive when only the Erdco tests are considered. The material, unfortunately, does not pass the water emulsion test. The data further show that neutral aluminum dihydroxy DNN sulfonate has superior properties as a thermal stability additive since it passes both the Erdco and water emulsion test.

The data presented in Table II show that commercial heating oil additives will not work as thermal stability additives for turbojet fuels. The concentrations tested for these materials were sixteen times greater than that which worked for the neutral aluminum dihydroxy DNN sulfonate.

While particular embodiments of the invention have been described, it will be understood, of course, that the invention is not limited thereto, since many modifications may be made; and it is, therefore, contemplated to cover by the appended claims any such modifications as fall Within the true spirit and scope of the invention.

The invention having thus been described, what is claimed and desired to be secured by Letters Patent is:

l. A liquid hydrocarbon jet fuel containing a minor amount, not greater than 0.0075 percent by weight, of aluminum dihydroxy dinonyl naphthalene sulfonate.

2. A liquid hydrocarbon jet fuel containing an amount, from about 0.0025 percent to about 0.0075 percent by weight, of aluminum dihydroxy dinonyl naphthalene sulfonate.

3. A liquid hydrocarbon jet fuel containing an amount, from about 0.0031 percent to about 0.0063 percent by weight, of aluminum dihydroxy dinonyl naphthalene sulfonate.

References Cited in the file of this patent UNITED STATES PATENTS 2,626,207 Wies et a] Jan. 20, 1953 2,695,910 Assefi et al Nov. 30, 1954 2,764,548 King et al Sept. 25, 1956 2,851,417 Andress Sept. 9, 1958 2,866,694 Glendenning et al Dec. 30, 1958 2,923,611 Wieland Feb. 2, 1960 

1. A LIQUID HYDROCARBON JET FUEL CONTAINING A MINOR AMOUNT, NOT GREATER THAN 0.0075 PERCENT BY WEIGHT, OF ALUMINUM DIHYDROXY DINONYL NAPHTHALENE SULFONATE. 